sdc: implement _crc16 in z80

The SD card driver is a bit too slow to be bearable. I'll write
_crc16 in z80 and see how it goes.

blk/226

@@ -10,4 +10,5 @@
 0xe6 OP2n ANDn,
 0xf6 OP2n ORn,
 0xd6 OP2n SUBn,
+0xee OP2n XORn,
 

blk/373

@@ -1,9 +1,16 @@
-CODE _sdcSel
-    SDC_CSLOW OUTnA,
+CODE _sdcSel SDC_CSLOW OUTnA, ;CODE
+CODE _sdcDesel SDC_CSHIGH OUTnA, ;CODE
+( Computes n into crc c with polynomial 0x1021 )
+CODE _crc16  ( c n -- c )
+    HL POPqq, ( n ) DE POPqq, ( c )
+    A L LDrr, D XORr, D A LDrr,
+    B 8 LDrn,
+    BEGIN,
+        E SLAr, D RLr,
+        IFC, ( msb is set, apply polynomial )
+            A D LDrr, 0x10 XORn, D A LDrr,
+            A E LDrr, 0x21 XORn, E A LDrr,
+        THEN,
+    DJNZ, AGAIN,
+    DE PUSHqq,
 ;CODE
-
-CODE _sdcDesel
-    SDC_CSHIGH OUTnA,
-;CODE
-
-

blk/377

@@ -1,15 +1,3 @@
-( c n -- c )
-( Computes n into crc c with polynomial 0x1021 )
-: _crc16
-    SWAP DUP 256 /    ( n c c>>8 )
-    ROT XOR           ( c x )
-    DUP 16 / XOR      ( c x^x>>4 )
-    SWAP 256 *        ( x c<<8 )
-    OVER 4096 * XOR   ( x c^x<<12 )
-    OVER 32 * XOR     ( x c^x<<5 )
-    XOR               ( c )
-;
-
 ( send-and-crc7 )
 ( n c -- c )
 : _s+crc SWAP DUP _sdcSR DROP _crc7 ;

blk/380

@@ -1,16 +1,16 @@
 : _err _sdcDesel ABORT" SDerr" ;
 
-( Initialize a SD card. This should be called at least 1ms
-  after the powering up of the card. )
-: SDC$
-( Wake the SD card up. After power up, a SD card has to receive
-  at least 74 dummy clocks with CS and DI high. We send 80. )
-    10 0 DO _idle DROP LOOP
-    ( call cmd0 and expect a 0x01 response (card idle)
-	  this should be called multiple times. we're actually
-      expected to. let's call this for a maximum of 10 times. )
-    0 ( dummy )
-    10 0 DO  ( r )
-        DROP 0x40 0 0 SDCMDR1  ( CMD0 )
-        DUP 0x01 = IF LEAVE THEN
-    LOOP 0x01 = NOT IF _err THEN                      ( cont. )
+( Tight definition ahead, pre-comment.
+
+  Initialize a SD card. This should be called at least 1ms
+  after the powering up of the card. We begin by waking up the
+  SD card. After power up, a SD card has to receive at least
+  74 dummy clocks with CS and DI high. We send 80.
+  Then send cmd0 for a maximum of 10 times, success is when
+  we get 0x01. Then comes the CMD8. We send it with a 0x01aa
+  argument and expect a 0x01aa argument back, along with a
+  0x01 R1 response. After that, we need to repeatedly run
+  CMD55+CMD41 (0x40000000) until the card goes out of idle
+  mode, that is, when it stops sending us 0x01 response and
+  send us 0x00 instead. Any other response means that
+  initialization failed. )

blk/381

@@ -1,10 +1,16 @@
-( Then comes the CMD8. We send it with a 0x01aa argument and
-  expect a 0x01aa argument back, along with a 0x01 R1
-  response. )
-    0x48 0 0x1aa  ( CMD8 )
-    SDCMDR7                     ( r arg1 arg2 )
+: SDC$
+    10 0 DO _idle DROP LOOP
+    0 ( dummy ) 10 0 DO  ( r )
+        DROP 0x40 0 0 SDCMDR1  ( CMD0 )
+        DUP 0x01 = IF LEAVE THEN
+    LOOP 0x01 = NOT IF _err THEN
+    0x48 0 0x1aa ( CMD8 ) SDCMDR7 ( r arg1 arg2 )
     0x1aa = NOT IF _err THEN      ( arg2 check )
     0 = NOT IF _err THEN          ( arg1 check )
     0x01 = NOT IF _err THEN       ( r check )
-
-                                                      ( cont. )
+    BEGIN
+        0x77 0 0 SDCMDR1  ( CMD55 )
+        0x01 = NOT IF _err THEN
+        0x69 0x4000 0x0000 SDCMDR1  ( CMD41 )
+        DUP 0x01 > IF _err THEN
+    NOT UNTIL ; ( out of idle mode, success! )

blk/382

@@ -1,13 +0,0 @@
-( Now we need to repeatedly run CMD55+CMD41 (0x40000000)
-  until the card goes out of idle mode, that is, when it stops
-  sending us 0x01 response and send us 0x00 instead. Any other
-  response means that initialization failed. )
-    BEGIN
-        0x77 0 0 SDCMDR1  ( CMD55 )
-        0x01 = NOT IF _err THEN
-        0x69 0x4000 0x0000 SDCMDR1  ( CMD41 )
-        DUP 0x01 > IF _err THEN
-    NOT UNTIL
-    ( Out of idle mode! Success! )
-;
-

tests/forth/test_sdc.fs

@@ -0,0 +1,10 @@
+212 LOAD ( z80a )
+: SDC_SPI 4 ;
+: SDC_CSLOW 5 ;
+: SDC_CSHIGH 6 ;
+372 LOAD ( sdc.z80 )
+374 LOAD ( sdc.fs )
+
+0x0000 0x00 _crc16 0x0000 #eq
+0x0000 0x01 _crc16 0x1021 #eq
+0x5678 0x34 _crc16 0x34e4 #eq